Fifth Mass Extinction: Cretaceous-Paleogene Extinction Event

The Cretaceous-Paleogene extinction event occurred 65 million years ago. In this extinction 17% of families, 50% of all genera, and 75% of all species became extinct. This extinction is believed to have been caused by an asteroid impact at the Chicxulub crater in the Yucatan plateau. Before this extinction, mammals were few and small, most resembling field mice. This extinction may have given rise to the reign of mammals.